Blower wheel assembly



Sept. 13, 1960 H. A. AUSTIN BLOWER WHEEL ASSEMBLY Filed April 12, 1957 3Sheets-Sheet l IN VEN TOR. Hmmzp A 40527 Sept- 1950 H. A. AUSTIN2,952,404

BLOWER WHEEL ASSEMBLY Filed April 12, 1957 3 Sheets-Sheet 2 Sept. 13,1960 H. A. AUSTIN 2,952,404

BLOWER WHEEL ASSEMBLY Filed April 12, 1957 3 Sheets-Sheet 3 INVEN TOR.

#42040 A Ausmv United States Patent 2,952,404 BLOWER WHEEL ASSEMBLYHarold A. Austin, Kalamazoo, Mich., assignor to Brundage Company,Kalamazoo, Mich., a corporation of Michigan Filed Apr. 12, 1957, Ser.No. 652,513

3'Claims. (Cl.230134) This invention relates to a blower wheel assemblyfor a multiblade centrifugal fan and more particularly to an improvedmounting for the blades on the frame of the blower wheel.

It has long been standard practice to use separately formed blades andto mount these blades on a frame to form a blower wheel. Many structureshave been proposed to effect such mounting. However, in spite of theprevious work in this field, the use of separately formed blades stillcreates problems in efiecting efiicient assembly of the blades to theblower wheel frame and also still creates problems as to the propermanner for achieivng mechanical balance and aerodynamic stability of theblower wheel.

Particularly, prior constructions of this general type have usuallyinvolved a large amount of hand work and have not lent themselvesreadily to automatic fabrica- 'tion methods. Further, many priorconstructions have operated so as to create excessive turbulence of thegas within the fan scroll. Such turbulence often results in excessivevibration and noise and likewise causes undesirably rapid wear of therunning parts of the fan. A contributing factor to this turbulence isbelieved to be the relatively bulky construction often appearing ateither axial end of the blower wheel and, in certain cases, by thenon-cylindrical construction of the blower wheels resulting from themethods of construction utilized therein. Thus, less gas is impelled bythe wheel at either end thereof than at the central portion of thewheelwhich causes creation of pressure diiferences within the fan scroll andthe resulting turbulence. Other known blower wheels of this generaltype, while initially satisfactory from the standpoint of turbulence andperformance, lack the rigidity and aerodynamic stability that isessential in equipment of this type. Thus, the blades or the blowerwheel frame may loosen and require frequent replacement.

Accordingly, it is a principal object of this invention to provide animproved blower wheel construction. t It is a further object of thisinvention to provide a blower wheel which is esesntially cylindrical inshape and which will create less turbulence of the gas within the fanscroll than do certain prior constructions.

It is a further object of this invention to provide a blower wheelconstruction in which the radially outer edges of the blades aresubstantially equidistant from the axis of rotation of the wheel.

It is a further object of this invention to provide a blower wheelconstruction in which the separately formed blades are rigidly andsecurely attached to the blower wheel frame and in which the blowerwheel operates at a low noise level and with a minimum of vibration.

It is a further object of this invention to provide a blower wheelassembly in which the blades are stressed in their assembly position onthe blower wheel frame .and in which the parts are balanced and stablein opera- .tion.

I A further object of the invention is to provide a blower 2,952,404Patented Sept. 13, 1950 2 wheel assembly, as aforesaid, in which thestressing of the blades takes place during the assembly of such wheeland, particularly, wherein the construction adapts the wheel to assemblyby automatic procedures, and the automatic and equal stressing of suchblades during the assem bly procedure.

It is a. further object of this invention to provide a blower wheelassembly which can be produced by high speed automatic machinery.

Other objects and advantages of this invention will be come apparent tothose acquainted with this type of equipment upon reading the followingdescription and inspecting the accompanying drawings.

In the drawings:

Figure 1 is an oblique, partially broken view of the blower wheelasesmbly which constitutes the subject of the present invention.

Figure 2 is a central, cross-sectional view of the blower wheel assemblysubstantially as shown in Fig urel.

Figure 3 is a sectional view taken along the line III-III of Figure 2.

Figure 4 is a broken, sectional view taken along the line IV-IV ofFigure 3.

Figure 5 is a sectional view taken along the line V-V of Figure 4.

Figure 6 is an oblique view of a blade in. its assembled condition, onthe wheel and showing an imaginary cylinder corresponding to the shapeof the assembled blower wheel, the shape of the blade being exaggeratedfor purposes of clear illustration thereof.

Figure 7 is a broken, plan' view of ablade blank prior to shaping.

General description The invention provides a blower wheel frame whichconsists of two annular end rims and a center structure which is securedto a shaft for rotation therewith. Notches are provided in the peripheryof the center structure to engage the blades. The blanks, from which theblades are made, are cut from sheet materialso that the lengthwise edges.of each blade define similar, wide angles lying in the plane of thesheet material. The blade blanks are then shaped to define a portion ofa cylinder, the axis of which is substantially parallel with thelengthwise extent of the blade blank. In the assembly of the blades uponthe frame, the blades are each placed with their convex edge closest tothe center of the wheel and positioned into the notches in the centerstructure. Pressure is then applied to both ends of the bladesurgf ingthem toward the center of the wheel. This causes said blades to assumepositions of stress wherein their inner and outer edges definesubstantially concentric cylinders. The ends of the blades are thensecured to the end rims. Detailed description The blower wheel assembly8 (Figures 1, 2 and 3) is comprised of a plurality of blades 18 whichare mounted upon a frame including a center structure 9 and a pair ofannular, end rims 10 and 11. The end rims, which are made of anysuitable material of. high tensile strength; are relatively narrow inradial extent and expose the radially inner, edge portions of theblades. This: com struction improves the operation and capacity of theblower wheel. a a

The center structure 9 is comprised of a pair of center plates 12 and 13which are in. this embodimentdisposed intermediate the rims 10 and 11.The center plates may be, and here are, identical with each other and,accord; ingly, only the center plate '13 will be described in detailfPlate 13 is generally circular in shape and is provided with a series,of, equally spaced notches 14 in the pea t p 'ythereof. ,The plateincludes an offset, center .por-

tion 15 which supports a hub 16. The hub secures the center plate to ashaft 17 for rotation of the plate with the-shaft.- .The center plates12- and '13 aregplaced'with' their; offset portions spaced from eachother anditheir respective notches '14 in alignment for receiving theblades therewithin. Said plates may be, but are not necessarily;fastened -together byfa'ny suitable means; as.' byfspot welding. TY" Aseries of blades 18 (Figures 2, 4 and 6-) are provided for assembly onthe blower wheel frame. Each blade is generally arcuate incross-sectional shape to prov1de a forwardly curved working surface inthis particular embodiment. The blades are notched at 19, which notch inthe assembled'position of the 'blades is received into a correspondingnotch 14 in the center structure 9Q The blade is provided with amounting flariger20 at each end thereof, which flange extends'generallyat a right angle to the lengthwise axis of the blade. The flange ispreferably integral with the blade and is preferably of the irregular,somewhat triangular, shape shown in Figures 5 and 7, which shapeprovides the maximum sup; port for the blades when they are mounted onthe.rims; In particular, the fold line or common edge 21 between theflange and the blade preferably is made as long as possible to contactthe maximum extent of the end edge of the arcuate blade. The length ofthe common edge axis than said adjacent points are.

the ends radially inwardly, with respect tothe wheel, until the inneredge 22 of the blade coincides with the line A. In such condition, thepoints on said edge 22, which are remote from the notch 19, will besubstantially the same distance from the axis of the center structure asthose points adjacent to the notch. It may be advantageous for the saidremote points to be further from said However, in no case will they becloser than said adjacent points. Thus, the blade is in a stressedcondition and remains so during the life of the Wheel. Because of theobtuse angle present in the formed blade, the application of force bythe force exerting tool will cause-the radially outer edge 23 of theblade to assume acondition where itis bowed forwardly in acircumferential direction (Figure 6) but in which all points of saidedge 23 lie at a substantially equal radial distance from the axis ofthe blower wheel. This is most clearly shown in-Figure 6 wherein theblade is shown with reference to a cylinderD which corresponds to thecylindrical shape of theblower wheel. .This figure illustrates in asomewhat exaggerated manner this-cir cumferential bowing of the outeredge 23, .which' in this embodiment has the ends leading the center ofthe blade,

21, which depends to some extent on the radial width of the rims 10 and11 and the positioning of 'the'blades thereon, is preferably at leastfifty' percent' of the'peripheral length of the end edge of the blade.This'construction of the flange gives maximum support to the blades andthereby insures maximum rigidity of the blower wheel assembly.

Asshow'n in Figure '7 in a somewhat exaggerated way, the blades arefabricated by punching blade blanks 18a from sheet metal. Thelongitudinal ends of the blade blanks 18a are normally contoured at eachend to provide the flanges 20 when in their assembled position on theframe. The lengthwise edges 22 and 23 of the blade blank are slightlyV-shaped and each define a pair of similar, obtuse angles of less than180 but usually over 179. In the preferred construction of the blank,both the radially-inner edge 22 and the radially outer edge 23 areparallel and hence are substantially equi-distant from each other. Thenotches 19, which-are located on the inner edge 22, are convenientlyprovided during the punch? mg of the blade by-a circular punch whichsimultaneously cuts a similar notch 19a in the outer edge 23 of thenextadjacent blade blank 18a. ,The blades are then shaped to form a part ofa cylinder, in this embodiment, having a single axis C extendinglongitudinally of the blade and parallelwith the lengthwise extentthereof, as indicated by the line A in Figures 4- and 7. Thus, the lineA represents a line parallel with the longitudinal axis of the assembledblower wheel whereas the line B (Figures 4 and 7) represents a lineparallel with the leftward halves of the radially inner and outer edgesof the blade 18 prior to assembly. The angle between the lines A and B,which determines the amount of the offset of the blade, preferably liesin the range of between about .07 or .30 of a degree.

The radially inner and outer edges of the rightward half of the blade,as appearing in Figure 2, lie at an equal but reverse angle with thelongitudinal axis of the assembled blower wheel when the blade is initslunassembled state. The end flanges 20 are bent along the lines 21into position for engaging the rims 10 and 11. f In assembly, the rims10-and 11 and the center plates 12 and 13 are mounted in fixed positionon a suitable fixture, not here shown. A blade 18 is then fed by handsaid leading being taken in the direction .ofrot-ation of the blowerwheel indicated by the arrow B. The actual amount of such leading issmall, being in oneembodi ment about & of an inch in a blade nineincheslong. The flanges 20 are then secured to the end rims 10 .and 11by suitable means which may be spot welding. The center structure andend rims are simultaneously rotated to a position where another blademay be mounted on the blower wheel frame in the manner described 'above.

7 This operation is repeated until all of the blades have been mountedon the frame.

When the blades are assembled to the blower wheel frame, the outer edge23 of each blade will liein, and define, a slight curve along thesurface of, a theoretical cylinder whose axis is concentric with theaxis of rotation of the wheel. Thus, the inner and outer edges 'ofeacliblade, when assembled may be substantially .equi-distant from the axisof the wheel while the outer edge 23. is bowed slightly in acircumferential direction,.which in this instance is the direction ofrotation; In addition; the flat end rims and the mounting flange 20 willpresent a relatively narrow end structure at eitherend of the blowerwheel. These two details of construction have been experimentallydetermined to minimize the turbulentfe of the gas within the blowerscroll and consequently. the. efliciency of a blower employing thisconstruction has bcen measurably increased thereby.- 1 This constructionand method of assembly causes the fan blades to be in a stressedcondition when in their assembled position. The blades in attemptingtorelieve this stress will exert a force on the rims 10 and 11. ,-How:ever, because of the equal spacing of the blades and symmetricalarrangement of the parts, the forces will be balanced and an extremelyrigid and stable structure. re-

' sults.

or suitable mechanism'so that notch 19 fits within one It may bedesirable under some conditions to'remove the above mentionedcircumferential bowing in the outer edge 23 of the assembled blade 18.This can be accomphshed by shaping the blade with slight dihedral. Sp'ecifically, the blade will be curvedin bothendwise: direc tions away fromthe axis of the theoretical cylinden' of which it is a part in the abovedescribed structure. 1 Thus, when a force is applied to the ends ofsaid'bladeto caulse its inner edge 22 to coincide with theline A, 'suchlfor ce will also move the outer edge. 23 into a" linefwhich; issubstantially parallel with said line vA. 1 F' 1 The said dihedral maybe limited to the'outer edge, or applied to both the inner and outeredges. Also, the dihedral. may be suflicient that it will not be oizhpleltely overcome. In such case, the blades will be circumferentiallyswept back with respect to .the direction of rotawardly directed 59:9?99 f blade to (5 ;.tion. These arrangements will providevariations'i'n'performance and may increase both the performance andefiiciency of the fan assembly.

Although I have disclosed particular, preferred embodiments of myinvention for illustrative purposes, it will be understood thatmodifications or variations thereof which lie within the scope of theinvention are fully contemplated unless specifically stated to thecontrary in the appended claims.

I claim:

1. In a centrifugal blower Wheel construction, the combinationcomprising: a pair of spaced and coaxial annular rims, a circular centerstructure of less diameter than the outside diameter of said spacedrims, a series of blades having radially inner and radially outer edges,both of said edges in their unstressed condition being spaced at theends of said blades radially outwardly of the respectively same edges inthe central portions of said blades, the radially inner edges of saidblades being engaged by the periphery of said center structureintermediate the ends of said blades, each of said rims being secured toopposite ends of said blades and exerting an inwardly directed force onthe ends of said blades and thereby holding said blades in a stressedcondition and tightly against said periphery, the radially inner andradially outer edges of said blades in the stressed condition of saidblades on rotation of the blower wheel de fining cylinders concentricwith the axis of rotation thereof, each cylinder having a constantradius throughout its length, and said center structure beingfrictionally held by said blades coaxial with said rims.

2. A centrifugal blower wheel according to claim 1 wherein each blade iscurved around a first axis parallel with said edges and the radiallyouter edge of each blade is curved about a second axis which extendsnormal to the axis of rotation of said blower wheel at the centerthereof; flange means integral with the ends of said blades andextending normal to the axis of rotation of said blower wheel andparallel to said rims, said flange means at the respective ends of saidblades being secured to the opposing surfaces of said rims.

3. A centrifugal blower wheel according to claim 1 wherein said rims areflat and said center structure has an outside diameter approximatelyequal to the inside diameter of said rims, said center structure havinga plurality of uniformly spaced notches in the periphery thereof and theinner edges of said blades being firmly disposed within said notches,each blade being curved around a first axis parallel with said edges.

References Cited in the file of this patent UNITED STATES PATENTS1,877,347 McMurdie Sept. 13, 1932 2,181,592 Sullivan Nov. 28, 19392,474,298 Zeidler June 28, 1949 2,495,855 Marcoe Jan. 31, 1950 2,537,805Wilken Jan. 9, 1951 2,626,741 Osborne Jan. 27, 1953 2,714,485 GoettlAug. 2, 1955 2,745,171 King et a1. May 15, 1956

